The present invention relates to a process for the preparation of aromatic aldehydes by the catalytic oxidation of aralkyl organic compounds such as toluene or substituted toluenes, preferably in the vapor phase. More particularly, the invention pertains to the reaction or aralkyl compounds with molecular oxygen in the presence of a supported catalyst containing phosphoric acid and palladium metal. The vapor phase process of the invention can be effectively employed, for example, the preparation of benzaldehyde from toluene.
Current industrial practice for the oxidation of toluene to benzaldehyde utilizes a uranium oxide/molybdenum oxide catalyst at about 500.degree.C. (W. L. Faith, D. B. Keyes and R. L. Clark, Industrial Chemicals, 3rd Ed., John Wiley & Sons, Inc., New York, 1965). It is among the objects of the present invention to provide a novel process for the selective production of aromatic aldehydes such as benzaldehyde or substituted benzaldehydes at relatively low temperatures.